It sounds like you're trying to say
X isn't needed unless your reader/listener doesn't know the definition of symptom.
Symptom is a basic enough word that If the reader doesn't know what it is he/she can consult a dictionary.
Symptoms are inauspicious ______ that might be caused by the induced sensations. But they can also be a sign of a latent or a manifest disease.
Symptoms might be caused by the induced sensations. But they can also be a sign of a latent or a manifest disease.
You can also provide examples this way if what you're really trying to do is narrow down the number of symptoms the reader/writer should be thinking about:
Symptoms such as X, Y, Z might be caused by the induced sensations. But they can also be a sign of a latent or a manifest disease.